France is preparing for the possible loss of its prized triple A credit rating, held since 1975, which the markets fear is possible despite last week's Brussels summit aimed at shoring up confidence in the eurozone.

Standard & Poor's warned France, Germany and 13 other eurozone members before last week's summit they faced a possible downgrade amid worsening economic conditions. But economists said France, which has been under the shadow of a downgrade for months, could fall further and faster than others despite the agreement reached in Europe on rules for budget-tightening.

France, the second-biggest economy in the eurozone, was the only AAA country singled out for a possible two-notch credit downgrade because of growth predictions seen as too optimistic, the threat of recession, budget cuts judged to be inadequate and the exposure of its banks to the sovereign debt crisis in Greece, Portugal, Italy and Spain.

A Reuters survey of 13 economists found 11 thought France would be downgraded by one of the major ratings agencies within the next three months. That would cause serious difficulties for Nicolas Sarkozy's 2012 re-election battle because he has staked his campaign on his personal ability to lead France out of the economic crisis.

A downgrade could push the government to hurriedly introduce a third austerity plan, after two rounds of limited budget cuts and tax rises in recent months. Unlike Britain, France has focused chiefly on tax rises rather than sweeping spending cuts. "If we lose the triple A, I'm dead," the president was recently reported saying in private.

A poll this weekend found just over half of French people feared a credit rating downgrade would have a big impact on their daily lives. A one-notch cut would hit the country with extra interest payments of up to €3bn (£2.5bn) a year if the markets react by pushing up bond yields.

The budget minister, Valerie Pecresse, attempted to calm the mood on Sunday, saying a downgrade "would make things more difficult' and "wouldn't be positive" but it would not change the government's economic policy on how to lift the deeply indebted French government out of the red after more than 30 years without balancing a budget.

"We work for the French people, not for the ratings agencies," she said. "No one doubts France's ability to pay back its debt."

She said an austerity plan that was "too violent" would risk harming growth and denied the government would need to bail out its biggest banks.